This circuit was found in a Popular Electronics from the 90s. It is based on components still common today and an optical coupler for the triac. The sensor is a thermistor.
This power supply also has a fine adjustment feature. The transformer is 16 + 16 V with 3 A and...
This circuit was obtained in a 1985s English magazine. The circuit can still be assembled with...
The circuit shown in the figure is suggested by Texas Instruments in its Linear Circuits...